That sense of doubt

Hi! I heard you've just got admission into a great university/received a big promotion/did really well in a difficult exam! You must be very pleased that your hard work paid off.
What's that you said? It wasn't hard work, just plain luck? No! Surely your own capabilities had something to do with it! You say you're not really that smart and have no idea how you managed this success? And you want to talk about the weather now? Why are you fidgeting about and trying to change the topic?
Hmm, sounds like you've got a case of imposter syndrome. First identified in the 1970s, this formidable-sounding term applies to high achievers who are nagged by a constant sense of doubt over their achievements. They attribute these achievements to luck or having "fooled" others about their competence, rather than to hard work, intelligence or merit. Instead of feeling pleased and accepting their successes, they believe that it is only a matter of time before they are discovered to be frauds.
Perfectionism
Now, being self-confident is not easy, and lots of people question their own abilities from time to time - when put into a new kind of challenge, or when faced with a situation that's not going the way they intended. However, people who experience Imposter Syndrome worry about messing up even in activities that they've historically been good at. This worry might manifest itself as striving for perfectionism in all aspects of their work, and hesitating to ask for help, for fear of how that might be viewed by others. Counter-productively, this worry also makes people more reluctant to try new things or take risks, thereby missing opportunities to do something they would be good at.
Imposter syndrome is not a formal diagnosis recognised in the Diagnostic and Statistical Manual of Mental Disorders (DSM, the go-to handbook of psychiatric disorders that is used by healthcare professionals). However, the feelings a person experiences in this syndrome need to be recognised and managed. Here are some ways to do this:
" Using an objective lens, write down the things you're good at. What are some of your achievements in the past few years that have been commendable? What are the situations in which people come to you for help or guidance?
" Be open to seeking help yourself. If there is someone who has more expertise in something than you do, there is no harm in asking that person for help. You are not expected to know everything or to have all the answers.
" Try not to compare yourself with others. Recognise that, while others might have strengths that you envy, they might also have weaknesses that you yourself can call a strength. Your co-worker may be great at coding but poor at making effective presentations, which is something that you might be good at.
" Accept that you can't be perfect at everything. You might feel pressure to build perfectionism into your work, but, realistically, there are not enough hours in the day to do this! Your aim should be to achieve perfection in a minority of activities, the ones that really matter. It's ok to be "good enough" for the remaining majority.
" Start thinking positive thoughts. Imposter syndrome might lead you to focus on the handful of things that went wrong, rather than the large number of things you got right.
Thinking positively is easier said than done. After all, you're training your brain to think in a different way than it is used to. There's no harm in getting the support of a psychologist for this. Therapies like Cognitive Behavioural Therapy (CBT) are all about helping you manage negative thoughts and actions.